How long should a person spend analyzing a game?

Until you've learnt every thing you

a) could

b) need

c) want to

from it. Choose one.

Yeah, like rooperi suggests, it's pretty much up to you (it's not an assignment or anything).

Let me put it this way:  if some Noted Authority told you you should analyze your games for an hour and an hour only, and you used up that hour and you still wanted to go on analyzing, would you stop anyway?  And if so...why?

Depends on the game. If it was a 5-mover, not much. Don't listen to advice such as "exactly one hour, 24 minutes and 15 seconds."